This homework asks you to show comprehension of
the concepts from lectures of the first two weeks.
Please read the homework by the 4th of February
so you can ask questions about it before I leave
town on the afternoon of the 4th.

Problem 1. Host d must be able to forward packets to every
host on LAN B, every host on LAN C, and also everyone in the Internet.
This can be done with three lines in the forwarding table, using
wildcard matching:

For IP address 128.205.64.0 with a mask of 24 bits (meaning
we only consider comparing on the first three bytes), a packet
should be forwarded onto Eth0.

For IP address 128.205.12.0 with a mask of 24 bits, a packet
with a matching destination address should be forwarded onto Eth1.

For IP address 0.0.0.0 with a mask of 0 bits (meaning any
address that doesn't match with the first two lines above), the
packet should be forwarded via the gateway at 128.205.12.1.

Note that the default line (the third line) doesn't have to specify
an interface (Eth0 or Eth1) because this is implied by the
gateway's IP address 128.205.12.1 matching the second line.

(You could also have a line for the loopback interface, such as

127.0.0.1 32 bits (no gateway) interface=loopback

if you wish, but it is not essential for answering the question.)

Problem 2

The IP packet in question is travelling from host e to host a.
Clearly, it has to be forwarded through d and through m in order
to reach a. We are only asked about the forwarding from d to m
for this question. So, the Ethernet frame sent from d to m
will have these data: